Didn't quite get what you mean, Asaf. If you're talking about HBASE-5349, please read release note of HBASE-5349.
By default, memstore min/max range is initialized to memstore percent: globalMemStorePercentMinRange = conf.getFloat( MEMSTORE_SIZE_MIN_RANGE_KEY, globalMemStorePercent); globalMemStorePercentMaxRange = conf.getFloat( MEMSTORE_SIZE_MAX_RANGE_KEY, globalMemStorePercent); Cheers On Wed, Apr 9, 2014 at 3:17 PM, Asaf Mesika <asaf.mes...@gmail.com> wrote: > The Jira says it's enabled by auto. Is there an official explaining this > feature? > > On Wednesday, April 9, 2014, Ted Yu <yuzhih...@gmail.com> wrote: > > > Please take a look at http://www.n10k.com/blog/blockcache-101/ > > > > For D, hbase.regionserver.global.memstore.size is specified in terms of > > percentage of heap. Unless you enable HBASE-5349 'Automagically tweak > > global memstore and block cache sizes based on workload' > > > > > > On Wed, Apr 9, 2014 at 12:24 AM, gortiz <gor...@pragsis.com<javascript:;>> > > wrote: > > > > > I've been reading the book definitive guide and hbase in action a > little. > > > I found this question from Cloudera that I'm not sure after looking > some > > > benchmarks and documentations from HBase. Could someone explain me a > > little > > > about? . I think that when you do a large scan you should disable the > > > blockcache becuase the blocks are going to swat a lot, so you didn't > get > > > anything from cache, I guess you should be penalized since you're > > spending > > > memory, calling GC and CPU with this task. > > > > > > *You want to do a full table scan on your data. You decide to disable > > > block caching to see if this** > > > **improves scan performance. Will disabling block caching improve scan > > > performance?* > > > > > > A. > > > No. Disabling block caching does not improve scan performance. > > > > > > B. > > > Yes. When you disable block caching, you free up that memory for other > > > operations. With a full > > > table scan, you cannot take advantage of block caching anyway because > > your > > > entire table won't fit > > > into cache. > > > > > > C. > > > No. If you disable block caching, HBase must read each block index from > > > disk for each scan, > > > thereby decreasing scan performance. > > > > > > D. > > > Yes. When you disable block caching, you free up memory for MemStore, > > > which improves, > > > scan performance. > > > > > > > > >